QUESTION: Can too much compost hurt plants?
ANSWER: With compost, as with fertilizer, it is possible to get too much and end up with an overabundance of nutrients in the soil, which can actually have a negative effect on plants. When you’re setting up garden beds in spaces that haven’t been cultivated before, a layer of one or two inches of compost worked down into the loosened soil is appropriate.
For beds that you’ve been working in, a thin layer of compost half an inch to one inch thick can be spread across the surface of garden soil and does not have to be worked into the soil underneath. You can also use compost on your lawn, though a lesser amount is required. Lawns can be fed with up to a quarter of an inch of compost each year.